Processes and systems for storing, distributing and dispatching energy on demand using and recycling carbon

ABSTRACT

The present invention generally relates to storing energy in a form that is carbon neutral, storable and transportable, so that it can be used on demand. The present invention provides a process and system for using energy as available to produce carbon from carbon oxide, and then oxidizing the carbon to generate useful energy on demand, while effectively recycling the carbon, oxidant, and carbon oxide used in the process or system. In one embodiment, the present invention effectively stores renewable energy as carbon, transports the carbon, oxidizes the carbon to generate useful energy on demand and recycles the carbon as carbon dioxide. This invention may increase the utilization of renewable energy, especially for electrical power generation, while producing no net carbon dioxide or other air pollutants.

PRIORITY DATA

This patent application claims the priority benefit of U.S. ProvisionalPatent Application No. 61/794,217, entitled “Process for Storing,Distributing and Dispatching Energy On Demand Using and RecyclingCarbon,” filed on Mar. 15, 2013, which is hereby incorporated byreference herein in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to processes and systems for thetransformation of energy as available into a form that is storable,distributable, and dispatchable as energy on demand.

BACKGROUND OF THE INVENTION

Existing energy production is based largely on combustion ofcarbon-based fuels derived from coal, crude oil, and natural gas.Although the earth has large deposits of these resources, their use isirreversible. In addition, one of the products of combustion is carbondioxide, which is currently thought to have negative effects on theearth's climate. Because coal, crude oil, and natural gas haveimpurities, their refining and use also generate pollutants, mostnotably mercury (primarily from coal), sulfur oxides, and nitrogenoxides.

Nuclear fission is an alternative source for producing energy. Undernormal circumstances, it does not produce carbon dioxide or other airpollutants. However, it does generate dangerous, highly toxic waste thatis difficult to manage. In addition, catastrophic failures can renderlarge areas of air, water, and land contaminated and unusable for longtime periods, from years to decades.

Renewable energy sources, such as biomass, wind, solar, and geothermalenergy, are constantly being replenished or produced in nature. Biomass,wind, and solar energy are all directly or indirectly produced fromsolar radiation. Geothermal energy is produced by thermal energy storedwithin the earth. These energy sources are practically inexhaustible. Inaddition, these energy sources do not inherently generate carbon dioxideor air pollutants by their use. Hence, renewable energy sources areattractive because they can potentially provide a sustainable, cleansupply of energy.

Unfortunately, most renewable sources are not available when and whereenergy is most needed. Currently the only effective means fortransporting energy long distances, other than fossil fuels, is aselectricity. Existing electricity technology, i.e. batteries, isexpensive and even less efficient, and transporting electricity storedin batteries long distances is currently impractical. Therefore,transporting renewable energy is limited by the transmissioncapabilities of the electric grid. Utilizing renewable energy that isremotely located from areas of greatest demand may not be feasible usingprocesses in the prior art.

Moreover, the times of greatest renewable generation and greatest demandmay not be the same. In some cases, the difference in time betweengreatest renewable generation and greatest demand can be half a year.There may be some means for converting electricity for storage for timesthis long, but the problem of electrical transmission capacity in realtime still applies unless the stored energy can be feasibly betransported. This lack of technically and economically feasible energyconversion and storage for renewable energy, especially for electricity,requires building excess conventional electric-generating capacity thatis underutilized to ensure that electric demand is satisfied at alltimes, while maximizing the use of renewable energy.

In addition, the location, time, and rate of available renewable energycannot be controlled. For instance, wind and solar power areintermittent and their rate depends on the intensity of wind or solarradiation. Furthermore, the location, time, and rate of energy demand donot generally match that of available renewable energy. For instance,the locations of greatest wind and solar power generation potential areoften distant from the locations of greatest energy demand, and theseason of greatest renewable energy production is often different fromthat of greatest energy demand. Therefore, meeting energy demand at alltimes requires having conventional generation capacity equal to themaximum coincident difference between demand and available renewableenergy. When the difference between demand and available renewableenergy is less than maximum, which is most of the time, conventionalgeneration capacity will be underutilized.

In some cases, renewable energy cannot be utilized, either becauseproviding enough transmission capacity for peak generation is noteconomically feasible, or because other sources of generated energy,such as hydro power, must be used instead.

Biomass is biologically produced matter. The chemical energy containedin biomass is derived from solar energy by the natural process ofphotosynthesis. This is the process by which plants take in carbondioxide and water from their surroundings and, using energy fromsunlight, convert them into carbohydrates. Biomass is, effectively,stored solar energy. However, biomass often decomposes easily and can bedifficult to store for long periods of time.

Other energy sources and energy carriers, except fossil fuels, are notstorable or are not storable for long periods of time. Nuclear fuelsdecay over time. Currently, the only practical means for storingelectricity is batteries. However, batteries are expensive andinefficient, and only store electricity for a limited time.

Although fuels, biomass, and electricity are transportable, many formsof energy are not feasibly so. In addition, the energy required totransport and distribute energy carriers limits how far and fast theycan be transported. Although electricity is transported quickly,transporting it is inefficient. For a form of energy to be practicallytransportable, it must have both sufficient specific energy, i.e. energyper unit mass, and energy density, i.e. energy per unit volume.Requirements for specific energy and energy density generally depend onthe end use of the energy carrier.

Hydrogen (H₂) has been proposed as an alternative energy carrier. Unlikeelectricity, hydrogen can be stored. It can also be transported.Hydrogen releases energy when oxidized to form water. In fact, hydrogenhas the greatest heat of combustion per mass (specific energy) of anycombustible fuel. In addition, the only product of hydrogen oxidationwith pure oxygen is water. Combustion in air may also generate somenitrogen oxides. Unfortunately, hydrogen is the least dense combustiblefuel. Consequently, at standard temperature and pressure, its heat ofcombustion per volume is only a fraction of that for fossil fuels. Infact, the heat of combustion per volume for hydrogen is only aboutone-third of that for methane, the main component of natural gas. Thelow energy density of hydrogen precludes its practical use astransportation fuel and limits its use for distributing energy and evenfor stationary energy storage.

Most of the proposed carbon-neutral energy carriers are hydrocarbons.The synthesis of these compounds from carbon oxide requires hydrogen,which is usually provided by water. Since water is a limited resource inhigh demand for other uses, the need for water to produce these fuels isa significant drawback with adverse environmental impacts.

In principle, carbon can be produced from virtually any materialcontaining carbon. Carbonaceous materials commonly include fossilresources such as natural gas, petroleum, coal, and lignite; andrenewable resources such as lignocellulosic biomass and variouscarbon-rich waste materials. Solid and liquid feedstocks (whetherfossil-based or renewable) can generally be converted to carbon-richmaterials by pyrolysis and related processes.

In view of the above-mentioned shortcomings, there are many needs in theart. It is desired to improve upon prior methods of storing anddispatching energy, i.e. to provide a better energy carrier, especiallyfor electrical power generation. It is desired to effectively storeelectrical energy for electrical load leveling, i.e. to match electricalgeneration with demand.

It is further desired to increase the utilization of renewable energysources, especially for electrical power generation, by renderingrenewable energy sources storable and dispatchable, thereby decreasingthe need for conventional energy sources to meet fluctuating energydemand. Being dispatchable, the energy carrier produced from renewableenergy can reduce the need for or even directly replace conventionalenergy sources.

Commercially, it is desired to decrease the cost of utilizing renewableenergy sources, especially for electrical power generation, bydecreasing the conventional energy generation capacity required to meetenergy demand and/or increasing the utilization thereof. It would bedesirable to store and dispatch energy, especially renewable energy, ina way that requires fewer changes to existing transportation and energygeneration, transmission, and distribution infrastructure thanalternative methods. It would be further desirable to store and dispatchenergy, especially renewable energy, in a way that improves on theoverall energy efficiency of alternative methods.

It is desired to facilitate distributed electrical power generation. Itis further desired to store and dispatch energy in a way that isrelatively safe. Additionally, it is desired to store and dispatchenergy in a way that effectively recycles the materials used, therebyreducing or eliminating the generation of byproducts with negativeenvironmental impacts, especially carbon dioxide and other greenhousegases.

Furthermore, it is desired to provide a source of reliable, affordableenergy for countries that lack adequate, economical conventional energysources, but have wind and solar resources.

SUMMARY OF THE INVENTION

By effectively making renewable energy dispatchable, variations of thisinvention decrease the maximum coincident difference between demand andavailable renewable energy. In addition, embodiments of this inventionincrease the utilization of conventional generation capacity bydecreasing the fluctuation in difference between demand and renewablesupplies. Both of these improvements decrease the cost of conventionalenergy generation required to consistently meet energy demand, whilestill utilizing renewable energy sources. In certain embodiments,renewable energy sources can completely replace conventional energysources while still meeting energy demand at all times. In addition,some embodiments of this invention increase the utilization of renewableenergy sources by storing generation that would have been wasted for useat a different time, and perhaps place.

Some variations of the invention provide a process for transformingenergy as available to energy on demand using the energy as available toreduce carbon oxide to carbon, separately oxidizing at least some of thecarbon to generate the energy on demand and consequent carbon oxide, andrecycling and/or reusing the consequent carbon oxide, either inactuality or virtually via the atmosphere.

In some embodiments, at least a portion of the carbon oxide is obtained,directly or indirectly, from the atmosphere. In these or otherembodiments, at least a portion of the carbon oxide is obtained from anindustrial process source.

The energy as available may be selected from the group consisting offossil-fuel energy, wind energy, solar energy, biomass energy,moving-water energy, geothermal energy, nuclear energy, and combinationsthereof. In preferred embodiments, the energy as available includesrenewable energy, or consists entirely of renewable energy.

In some embodiments, the energy as available directly provides energy,heat, or work to reduce the carbon oxide to the carbon. In someembodiments, the energy as available is converted to secondary energy,and the secondary energy provides energy, heat, or work to reduce thecarbon oxide to the carbon. The secondary energy is electricity, incertain embodiments.

The energy as available may directly or indirectly provide at least aportion of the carbon oxide to the process. For example, the energy asavailable may be biomass energy, which is generally associated withgeneration of carbon dioxide. In that case, the carbon dioxide may beused as, or combined with, the carbon oxide. Also the biomass energy maybe associated with carbon monoxide, such as when biomass is gasified, inwhich case the carbon monoxide may be used as, or combined with, thecarbon oxide.

The carbon oxide may be converted to a reduced stream comprising thecarbon and an oxidant in a reduction reactor operated at effectivereduction conditions. In some embodiments, the reduced stream consistsessentially of carbon and an oxidant.

In various embodiments, the effective reduction conditions are providedby chemical, catalytic, thermal, electrical, dielectrical, ionic,plasma, electrochemical, electromagnetic, or photocatalytic means, or acombination thereof. In preferred embodiments, the effective reductionconditions are provided by electrons, photons, plasma, or combinationsthereof. In some embodiments the extent of the reduction conditions maybe varied or pulsed during the course of the reduction process.

The reduction reactor may be selected from the group consisting of athermal reactor, a catalytic reactor, an electrolysis reactor, a reversefuel cell, an electrochemical reactor, an electromagnetic reactor, aphotocatalytic reactor, a pulsed laser reactor, and a plasma reactor,and combinations thereof.

In some embodiments, the carbon oxide comprises carbon monoxide, and theeffective reduction conditions promote the carbon-forming Boudouardreaction.

Alternatively, or additionally, the carbon oxide may be reduced with ametal/metal oxide to generate the carbon and a further reduced metaloxide in a reduction reactor operated at effective reduction conditions.In these embodiments, the effective reduction conditions may be providedby chemical, catalytic, thermal, electrical, ionic, plasma,electrochemical, electromagnetic, or photocatalytic means, or acombination thereof.

In these embodiments, the reduction reactor may be selected from thegroup consisting of a thermal reactor, a catalytic reactor, anelectrolysis reactor, a reverse fuel cell, an electrochemical reactor,an electromagnetic reactor, a photocatalytic reactor, a pulsed laserreactor, and a plasma reactor.

In any of these embodiments, the carbon oxide may be reduced to thecarbon continuously, semi-continuously, or batchwise.

When the carbon oxide is converted to a stream(s) comprising carbon andan oxidant in a reduction reactor, the process optionally comprisesseparating the carbon from the oxidant in a separation unit that may beseparate from, or integrated with, the reduction reactor.

In some embodiments, the carbon is amorphous carbon. In these or otherembodiments, the carbon is densified (e.g., agglomerated, pelletized, orcompressed) to increase its bulk density for more efficient handling.

In certain embodiments, the process further comprises supplementing thecarbon with another carbon source, initially and/or continuously.

In some embodiments, the process further comprises transporting at leasta portion of the carbon to an oxidation reactor. In certain embodiments,all of the carbon is transported to the oxidation reactor. The carbonmay be transported by a transporting means selected from the groupconsisting of truck, train, ship, barge, pipeline, bulk solids conveyer,and combinations thereof.

In some particular embodiments, the carbon is transported by forming aslurry of carbon in liquid oxygen. The liquid oxygen may be derived fromreduction of the carbon oxide to the carbon.

In some embodiments, the process further comprises intermediate storageof the carbon. The intermediate storage of the carbon may be located ata site associated with the energy as available, a site associated withthe energy on demand, or both of these. Some other location may be usedfor intermediate storage of the carbon, if desired. The intermediatestorage may be selected from the group consisting of piles, rail cars,truck trailers, tanks, silos, bins, hoppers, intermediate bulkcontainers, sacks, drums, and combinations thereof.

Some embodiments do not physically transport carbon to another location.For example, a common reactor may be utilized to reduce the carbon oxideto the carbon and then later to oxidize the carbon to the consequentcarbon oxide.

In preferred embodiments, the carbon is oxidized with an oxidant. Thecarbon may be oxidized with oxygen, which may be obtained from airand/or from the reduction of the carbon oxide to carbon and oxygen.Alternatively, or additionally, the carbon may be oxidized with a metaloxide or another compound containing a metal and oxygen, such as a metalhydroxide.

Some embodiments further comprise transporting the oxidant from areduction reactor to an oxidation reactor. Optionally, intermediatestorage of the oxygen-containing compound is included, such as at a siteassociated with the energy as available, or at a site associated withthe energy on demand, or both of these. Storage of the oxidant may beselected from the group consisting of a piles, rail cars, trucktrailers, tanks, silos, bins, hoppers, intermediate bulk containers,sacks, drums, the atmosphere, and combinations thereof, for example.

In some embodiments, the intermediate storage of the oxidant is locatedat a storage site that is not co-located with sites associated with theenergy as available or the energy on demand.

The oxidation of the carbon will typically (although not necessarily) becarried out in an oxidation reactor operated at effective oxidationconditions to generate reaction energy and an oxidized stream comprisingthe consequent carbon oxide. Exemplary oxidation reactors include, butare not limited to, a boiler, a conventional coal-fired power plant, amodified coal-fired power plant, a non-catalytic combustion unit, acatalytic oxidation reactor, a chemical-loop combustion system, a fuelcell, a combined heat and power system, and an integrated gasificationcombined cycle unit. In some embodiments, the oxidation reactor is amolten carbonate or solid oxide fuel cell.

Some or all of the carbon may be oxidized to generate the energy ondemand and the consequent carbon oxide. The reaction energy may bedirectly recovered as the energy on demand. Alternatively, oradditionally, the reaction energy may be converted to the energy ondemand. The energy on demand may be selected from the group consistingof electrical energy, mechanical energy, thermal energy, chemicalenergy, electromagnetic energy, and combinations thereof. In preferredembodiments, the energy on demand is dispatchable and distributablerenewable energy.

Preferably, at least 50% of the carbon oxide is provided by therecycling and/or reusing the consequent carbon oxide. More preferably,at least 90% of the carbon oxide is provided by the recycling and/orreusing the consequent carbon oxide. Most preferably, all of the carbonoxide is provided by the recycling and/or reusing the consequent carbonoxide. In addition, in certain embodiments, essentially all (except forprocess losses) of the consequent carbon oxide is recycled and/orreused. Any of these recycling and/or reusing scenarios may be achievedin actuality or virtually.

The consequent carbon oxide may be recycled and/or reused in actuality.Alternatively, or additionally, the consequent carbon oxide, as carbondioxide, may be recycled and/or reused virtually via the atmosphere. Anycombination or ratio of carbon oxide recycled or reused actually, versusthat recycled or reused virtually, may be employed.

In some embodiments, the process further comprises intermediate storageof the consequent carbon oxide. The intermediate storage of theconsequent carbon oxide may be located at a site associated with theenergy on demand and/or at a site associated with the energy asavailable. In some embodiments, the intermediate storage of theconsequent carbon oxide is located at a carbon oxide storage site thatis not co-located with sites associated with the energy as available orthe energy on demand. For example, the carbon oxide storage may beselected from the group consisting of rail cars, truck trailers, tanks,silos, bins, hoppers, intermediate bulk containers, sacks, drums, theatmosphere, and combinations thereof.

The energy as available sub-system may be co-located with the energy ondemand sub-system at a single plant site. Or, the energy as availablesub-system and the energy on demand sub-system may be located atseparate sites.

In preferred embodiments of the invention, the process generatesessentially no net carbon emissions (as carbon itself or as carbonoxide). Again, the attainment of no net carbon may be achieved inactuality or virtually.

Some embodiments provide a process for transforming renewable wind orsolar energy as available to dispatchable energy on demand, the processcomprising:

-   -   (a) using the renewable wind or solar energy as available, in        thermal, electron, photon, or plasma form, to reduce carbon        oxide to carbon and oxygen;    -   (b) increasing bulk density of the carbon;    -   (c) separately oxidizing at least some of the carbon to generate        the energy on demand and consequent carbon oxide; and    -   (d) recycling and/or reusing the consequent carbon oxide, either        in actuality or virtually via the atmosphere,    -   wherein the process is characterized by essentially zero net        carbon emissions.

The present invention also provides systems and apparatus for carryingout the processes disclosed. Some embodiments provide a system thattransforms energy as available to energy on demand, the systemcomprising a first sub-system to use the energy as available to reducecarbon oxide to carbon, a second sub-system to separately oxidize atleast some of the carbon to generate the energy on demand and consequentcarbon oxide, and means for recycling and/or reusing the consequentcarbon oxide, either in actuality or virtually via the atmosphere.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a process block-flow diagram depicting various embodiments ofthe invention, to reduce carbon oxide and separately oxidize carbon toproduce useful energy.

FIG. 2 is a process block-flow diagram depicting some embodiments of theinvention, to transform energy as available to energy on demand.

FIG. 3 is a process block-flow diagram depicting some embodiments of theinvention utilizing supplemental carbon.

FIG. 4 is a process block-flow diagram depicting some embodiments of theinvention utilizing metals and oxides.

FIG. 5 is a process block-flow diagram depicting some embodiments of theinvention utilizing supplemental carbon oxide.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

This description will enable one skilled in the art to make and use theinvention, and it describes several embodiments, adaptations,variations, alternatives, and uses of the invention. These and otherembodiments, features, and advantages of the present invention willbecome more apparent to those skilled in the art when taken withreference to the following detailed description of the invention inconjunction with the accompanying drawings.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contextclearly indicates otherwise. Unless defined otherwise, all technical andscientific terms used herein have the same meaning as is commonlyunderstood by one of ordinary skill in the art to which this inventionbelongs.

Unless otherwise indicated, all numbers expressing reaction conditions,stoichiometries, concentrations of components, and so forth used in thespecification and claims are to be understood as being modified in allinstances by the term “about.” Accordingly, unless indicated to thecontrary, the numerical parameters set forth in the followingspecification and attached claims are approximations that may varydepending at least upon a specific analytical technique.

The term “comprising,” which is synonymous with “including,”“containing,” or “characterized by” is inclusive or open-ended and doesnot exclude additional, unrecited elements or method steps. “Comprising”is a term of art used in claim language which means that the named claimelements are essential, but other claim elements may be added and stillform a construct within the scope of the claim.

As used herein, the phrase “consisting of” excludes any element, step,or ingredient not specified in the claim. When the phrase “consists of”(or variations thereof) appears in a clause of the body of a claim,rather than immediately following the preamble, it limits only theelement set forth in that clause; other elements are not excluded fromthe claim as a whole. As used herein, the phase “consisting essentiallyof” limits the scope of a claim to the specified elements or methodsteps, plus those that do not materially affect the basis and novelcharacteristic(s) of the claimed subject matter.

With respect to the terms “comprising,” “consisting of,” and “consistingessentially of,” where one of these three terms is used herein, thepresently disclosed and claimed subject matter may include the use ofeither of the other two terms. Thus in some embodiments not otherwiseexplicitly recited, any instance of “comprising” may be replaced by“consisting of” or, alternatively, by “consisting essentially of.”

For purposes of this patent application, “carbon oxide” means carbonmonoxide (CO), carbon dioxide (CO₂), or any combination of carbonmonoxide and carbon dioxide. In embodiments of the invention involvingtransport of carbon oxide or release of carbon oxide to the atmosphere,carbon oxide will typically be carbon dioxide. Carbon oxide may be agas, liquid, or solid, depending on the process step and the embodimentof the invention, but carbon oxide is preferably a gas.

“Carbon” means elemental carbon in any form, recognizing that impuritiesmay be present in the carbon physically and/or chemically. Carbon mayinclude a mixture of allotropes, possibly in combination with othermaterials. Carbon is preferably dense, free-flowing, particulates ofamorphous carbon.

As intended in this patent, an “oxidant” means any form of the elementoxygen, which may be combined with another element or compound, andwhich may be present in a mixture of other species. For example, withoutlimitation, an oxidant may be oxygen as defined in this patent, anoxide, or a metal oxide. The oxidant may be a gas, liquid or solid,depending on the process step and the embodiment of the invention. Whenthe oxidant is oxygen, it may be utilized as a component of air.

“Oxygen” is any form of the element oxygen, preferably diatomicmolecular form (O₂), optionally ozone (O₃), ionized oxygen or oxygenradicals. Oxygen may be a gas, liquid or solid, depending on the processstep and the embodiment of the invention, but is preferably a gas. Ifoxygen is stored and transported, it is preferably a liquid. Oxygen maybe utilized as a component of air, which is the gaseous mixture thatcomprises the atmosphere, primarily nitrogen and oxygen, with smallerconcentrations of water, carbon dioxide, and other gases.

An “energy source” may be any form of energy, generally a primary energysource or electricity. An energy source is preferably a renewable energysource, but may be any other form of energy including fossil-fuelenergy, nuclear energy, and so on.

A “primary energy source” is energy found in nature that has not beensubjected to any conversion or transformation process, includingunprocessed fossil and nuclear fuels, biomass, wind, solar, moving waterand geothermal energy.

“Secondary energy” is an optional form of energy generated from theenergy source. Secondary energy is generally thermal, electrical ormechanical energy, but may be other forms of energy.

“Useful energy” is the final desired form of energy, generally, but notlimited to, electricity, heat or mechanical energy, depending on thefinal use for the energy. Useful energy produced by the invention mayrequire or benefit from further steps, such as transmission and/ordistribution to be delivered for use. Alternatively or additionally,useful energy may be used to perform work directly.

“Energy as available” means an energy source, typically a primary energysource, that may be utilized directly or indirectly to carry out carbonoxide reduction. An “energy as available sub-system” means a sub-system,in an overall system, that includes energy as available and means forreducing carbon oxide to carbon (see, for example, upper box of FIG. 2).Note that the location of energy as available may be the same ordifferent than the location of the carbon oxide reduction.

“Energy on demand” means useful energy that is recovered, directly orindirectly, from reaction energy derived from carbon oxidation. An“energy on demand sub-system” means a sub-system, in an overall system,that includes energy on demand and means for capturing reaction energyfrom carbon oxidation (see, for example, lower box of FIG. 2). Note thatthe location of energy on demand may be the same or different than thelocation of the carbon oxidation.

When the carbon oxide, carbon and/or oxidant are transported, the“theoretical effective specific energy” is the theoretical usable energyper mass based on the exothermic heat of reaction of the “oxidizecarbon” step and the total mass of transported reactants (or inputs) andproducts (or outputs). Likewise, “theoretical effective energy density”is the theoretical usable energy per volume based on the exothermic heatof reaction of the “oxidize carbon” step and the total volume oftransported reactants (or inputs) and products (or outputs).

Some variations of the invention are premised on the realization thatenergy as available may be effectively transformed to energy on demand,by reusing and/or recycling carbon in overall processes and systemsdescribed herein. In particular, carbon may first be generated fromcarbon oxide, followed by oxidizing that carbon with an oxidant (such asoxygen) to generate useful energy on demand, and recycling theconsequent (from carbon oxidation) carbon oxide, either in actuality orvirtually via the atmosphere. It has been discovered that such processesmay be configured to generate essentially no net carbon dioxide or airpollutants. In some embodiments, the carbon, the oxidant, and carbonoxide are all reused and/or recycled materials within the process.

Most proposed energy carriers are either liquid or gaseous fuels. Thismakes sense because fluids are generally easier to store, handle, andtransport than solids. However, the least expensive fuel to transportmust have both high specific energy and high energy density. Althoughthe specific energy of combustion of carbon (32.8 MJ/kg) is less thanthat of hydrogen (142 MJ/kg), methane (55.5 MJ/kg), and octane (47.9MJ/kg), it is double that of biomass (15.6 MJ/kg as glucose); and theenergy density of combustion of carbon (55.7 GJ/m³, based on solidamorphous carbon) is greater than that of hydrogen (0.0128 GJ/m³),methane (0.0398 GJ/m³), octane (33.7 GJ/m³), and biomass (24.0 GJ/m³ asglucose). Since the specific energy and energy density of carbon areboth comparable to octane, which is a surrogate for gasoline, carbon isa good candidate for an energy carrier.

Generally speaking, producing carbon requires a carbon-containingfeedstock and energy to extract carbon from that feedstock. Thecarbon-containing feedstock could be fossil fuels (e.g., hydrocarbons orcoal), biomass, carbonates in rocks, carbon monoxide, or carbon dioxide.Carbon dioxide exists naturally in water and air. High concentrations ofcarbon dioxide are typically present in combustion products from burningfossil fuels, especially from burning coal.

“Biomass,” for purposes of this disclosure, shall be construed as anybiogenic feedstock or mixture of a biogenic and non-biogenic feedstock.Elementally, biomass includes at least carbon, hydrogen, and oxygen.Biomass includes, for example, plant and plant-derived material,vegetation, agricultural waste, forestry waste, wood waste, paper waste,animal-derived waste, poultry-derived waste, and municipal solid waste.In various embodiments of the invention utilizing biomass, the biomassfeedstock may include one or more materials selected from: timberharvesting residues, softwood chips, hardwood chips, tree branches, treestumps, knots, leaves, bark, sawdust, off-spec paper pulp, green orblack liquor from paper pulping, cellulose, corn, corn stover, wheatstraw, rice straw, sugarcane bagasse, switchgrass, miscanthus, animalmanure, municipal garbage, municipal sewage, commercial waste, grapepumice, almond shells, pecan shells, coconut shells, coffee grounds,grass pellets, hay pellets, wood pellets, cardboard, paper,carbohydrates, plastic, and cloth.

Various embodiments of the present disclosure may also be used forcarbon-containing feedstocks other than biomass, such as a fossil fuel(e.g., coal or petroleum coke), or any mixtures of biomass and fossilfuels (such as biomass/coal blends). In some embodiments, a biogenicfeedstock is, or includes, coal, oil shale, crude oil, asphalt, orsolids from crude-oil processing (such as petcoke). Feedstocks mayinclude waste tires, recycled plastics, recycled paper, and other wasteor recycled materials. Any process, apparatus, or system describedherein may be used with any carbonaceous feedstock. Carbon-containingfeedstocks may be transportable by any known means, such as by truck,train, ship, barge, tractor trailer, or any other vehicle or means ofconveyance.

Variations of the invention utilize and recycle carbon, oxygen, andcarbon oxide as materials to store and transfer energy from renewableenergy sites to sites of energy generation and use on demand, therebyproviding a sustainable, carbon-neutral energy storage and transfersystem. This sustainable chemical energy conversion and storage systemcan minimize the costs to transport and distribute renewable energy.

At or near a renewable energy source, generated energy may be used toproduce carbon from carbon oxide according to the chemical equation (inembodiments producing molecular oxygen):CO_(x)+energy→C+0.5xO₂This reaction is an endothermic reduction of carbon oxide to carbon andoxygen. The reduction step will be further discussed below, includingalternative embodiments.

The carbon may be collected, stored, and transported to energygeneration sites or points of use. The oxygen may be transported toenergy generation sites and points of use for oxidation of the carbon.Optionally, the oxygen may be exhausted to atmosphere, and/or collectedfor other uses.

At the energy generation sites or points of use, the carbon is oxidizedwith an oxidant, such as air or oxygen, to produce carbon oxide,according to the equation (when the oxidant is oxygen or air):C+0.5xO₂→CO_(x)+energyThis reaction is exothermic oxidation of carbon to produce carbon oxide.The oxidation step will be further discussed below, includingalternative embodiments. The energy of reaction is the heat ofcombustion, i.e. the energy released from the oxidation of carbon. Theenergy of reaction could take one of several different forms dependingon the means used to perform the oxidation. If the means of oxidation iscombustion, the energy of reaction is heat. If the means of oxidation iselectrochemical, at least some of the energy of reaction is electricity.

The carbon oxide is either collected and transported back to therenewable energy generation site or, as CO2, is exhausted to atmosphere.If the carbon oxide is exhausted to atmosphere, the renewable energysites may utilize carbon dioxide from air or combustion of biomass inorder for the overall system to be sustainable with no net generation ofcarbon dioxide into the atmosphere. Such a virtual system is describedin more detail below.

By effectively making renewable energy dispatchable, variations of thisinvention decrease the maximum coincident difference between demand andavailable renewable energy. In addition, embodiments of this inventionincrease the utilization of conventional generation capacity bydecreasing the fluctuation in difference between demand and renewablesupplies. Both of these improvements decrease the cost of conventionalenergy generation required to consistently meet energy demand, whilestill utilizing renewable energy sources. In certain embodiments,renewable energy sources can completely replace conventional energysources while still meeting energy demand at all times. In addition,some embodiments of this invention increase the utilization of renewableenergy sources by storing generation that would have been wasted for useat a different time, and perhaps place.

Some variations of the invention provide a process for transformingenergy as available to energy on demand using the energy as available toreduce carbon oxide to carbon, separately oxidizing at least some of thecarbon to generate the energy on demand and consequent carbon oxide, andrecycling and/or reusing the consequent carbon oxide, either inactuality or virtually via the atmosphere.

In some embodiments, at least a portion of the carbon oxide is obtained,directly or indirectly, from the atmosphere (typically as CO₂). Carbondioxide may be recovered directly from the atmosphere by separationmeans, such as cryogenic distillation, scrubbing, membrane filtration,zeolite separation, moisture-swing absorption, and so on. Carbon dioxidemay be recovered directly from the atmosphere by scrubbing with calciumoxide or sodium hydroxide, for example. Carbon dioxide may be recovereddirectly from the atmosphere by reacting directly with a metal/metaloxide to form a metal oxide and carbon. Carbon dioxide may be recoveredindirectly from the atmosphere by various means, including as renewablebiomass with accounting of net CO₂, as will be described in more detailbelow.

Eisaman, et al., “Carbon-neutral liquid fuel from sunlight, air, andwater,” Gordon Research Conference on Renewable Energy: Solar Fuels,2009, is hereby incorporated by reference herein. Eisaman discloseselectrochemical methods for separating CO₂ from air for the purpose ofproducing carbon-neutral liquid fuel using only sunlight, air, andwater. Using a modified-fuel-cell approach, the authors havedemonstrated CO₂ separation from atmospheric concentrations with anenergy consumption of less than 400 kJ/mol (CO₂).

In these or other embodiments, at least a portion of the carbon oxide isobtained from an industrial process source (which may be CO or CO₂).There are many industrial process sources of CO or CO₂, such as powerplants, refineries, biorefineries, food plants, pulp and paper plants,fermentation processes, metal processes, and so on.

The energy as available may be selected from the group consisting offossil-fuel energy, wind energy, solar energy, biomass energy,moving-water energy, geothermal energy, nuclear energy, and combinationsthereof. In preferred embodiments, the energy as available includesrenewable energy, or consists entirely of renewable energy.

In some embodiments, the energy as available directly provides energy,heat, or work to reduce the carbon oxide to the carbon. In someembodiments, the energy as available is converted to secondary energy,and the secondary energy provides energy, heat, or work to reduce thecarbon oxide to the carbon. The secondary energy may be electricity, incertain embodiments, such as when the energy as available is solar orwind power.

The energy as available may directly or indirectly provide at least aportion of the carbon oxide to the process. For example, the energy asavailable may be biomass energy that is associated with generation ofcarbon oxide, either carbon dioxide (when fully oxidized) or carbonmonoxide (when partially oxidized, e.g. during gasification). Suchcarbon oxide may be used as the starting source of carbon oxide, or itmay be combined with other carbon oxide.

The carbon oxide may be converted to (a) reduced stream(s) comprisingthe carbon and oxygen in a reduction reactor operated at effectivereduction conditions. In some embodiments, the reduced stream(s)consists essentially of carbon and oxygen.

In various embodiments, the effective reduction conditions are providedby chemical, catalytic, thermal, electrical, ionic, plasma,electrochemical, electromagnetic, or photocatalytic means, or acombination thereof. In preferred embodiments, the effective reductionconditions are provided by electrons, photons, plasma, or combinationsthereof.

The reduction reactor may be selected from the group consisting of athermal reactor, a catalytic reactor, an electrolysis reactor, a reversefuel cell, an electrochemical reactor, an electromagnetic reactor, aphotocatalytic reactor, a pulsed laser reactor, and a plasma reactor,and combinations thereof.

In some embodiments, the carbon oxide comprises carbon monoxide, and theeffective reduction conditions promote the carbon-forming Boudouardreaction:2CO→C+CO₂The CO₂ produced may then be reduced to carbon and oxygen (or anotheroxygen-containing material). The Boudouard reaction is promoted by highpressures and relatively low temperatures (compared to temperatures forcarbon oxide reduction). In some embodiments, the Boudouard reaction isonly important in certain regions of a reactor or other unit, in whichfor example there are localized cool spots.

Alternatively, or additionally, the carbon oxide may be reduced with ametal/metal oxide to generate the carbon and a metal oxide in areduction reactor operated at effective reduction conditions. In theseembodiments, the effective reduction conditions may be provided bychemical, catalytic, thermal, electrical, ionic, plasma,electrochemical, electromagnetic, or photocatalytic means, or acombination thereof.

In these embodiments, the reduction reactor may be selected from thegroup consisting of a thermal reactor, a catalytic reactor, anelectrolysis reactor, a reverse fuel cell, an electrochemical reactor,an electromagnetic reactor, a photocatalytic reactor, a pulsed laserreactor, and a plasma reactor.

An exemplary pulsed laser reactor is disclosed in Fukuda, et al., NewJournal of Physics 9 (2007) 321, which is hereby incorporated byreference herein. Fukuda discloses a reactor for dissociating CO₂ to Cand O₂ at near critical conditions, 31° C. and 7.38 MPa. Operating nearroom temperature, the reactor uses a pulsed UV laser coupled with anelectric field to produce carbon on the electrodes.

An exemplary plasma reactor is disclosed in DE102009048541 to Hosbach,et al., which is hereby incorporated by reference herein. Hosbachdiscloses a plasma reactor that uses electrodes with an intermittent,pulsed electrical potential to dissociate CO₂ into C and O₂.

In any of these embodiments, the carbon oxide may be reduced to thecarbon continuously, semi-continuously, or batchwise. That is, theenergy as available sub-system may be operated continuously,semi-continuously, or batchwise. Also, the energy on demand sub-systemmay be operated continuously, semi-continuously, or batchwise. The modeof operation of the energy as available sub-system is independent fromthat of the energy on demand sub-system. For example, the energy asavailable sub-system could operate semi-continuously while the energy ondemand sub-system operates continuously. Or each sub-system couldoperate essentially in batchwise mode, with the overall system operatingsemi-continuously or pseudo-continuously. It should be also noted thatsome embodiments employ sequential batches in the same reactor orvessel, i.e., carbon oxide reduction to carbon and then later carbonoxidation, without necessarily removing the carbon and withoutnecessarily moving the reactor or vessel.

When the carbon oxide is converted to a reduced stream comprising carbonand oxygen in a reduction reactor, the process optionally comprisesseparating the carbon from the oxygen in a separation unit that may beseparate from, or integrated with, the reduction reactor. When thecarbon oxide is reduced with a metal/metal oxide to generate the carbonand a metal oxide in a reduction reactor, the process optionallycomprises separating the carbon from the metal oxide in a separationunit that may be separate from, or integrated with, the reductionreactor.

For example, see WO 2011/050437 (Cundliffe), which is incorporated byreference herein. Cundliffe discloses a thermo-electric-dielectricreactor for reducing carbon oxide to C and O₂ at industrial scale. Thereactor has a working zone where CO or CO₂ is dissociated to ionic C andO by simultaneous heating and subjection to an electric field. The ionicO is separated, ultimately forming O₂. The reactor also has a transitionzone and a carbon collection zone where carbon is condensed from thegaseous stream. Reactor pressure ranges from 0.07-9.65 MPa. Working zoneconditions are 1,000-2,400° C. and 10-150 amps. The carbon collectionzone temperature is at least 700° C. less than the working zone,approximately 300-800°, most preferably 0-300° C.

In some embodiments, the carbon is amorphous carbon. In these or otherembodiments, the carbon is densified (e.g., agglomerated, pelletized, orcompressed) to increase its bulk density for more efficient handling.Other allotropes of carbon may be present, such as graphite, graphene,carbon nanostructures, etc. Other components may be present with thecarbon, such as solid impurities from processes (e.g., ash), or otherelements (e.g., hydrogen, nitrogen, sulfur, etc.).

The composition of the carbon will typically be primarily C itself, butgenerally speaking the carbon will comprise at least 85 wt %, at least90 wt %, at least 95 wt %, at least 96 wt %, at least 97 wt %, at least98 wt %, or at least 99 wt % carbon.

In certain embodiments, the process further comprises supplementing thecarbon with another carbon source, initially and/or continuously. Thisother carbon source may be introduced to the carbon derived from thecarbon reduction step, prior to the carbon oxidation step. The othercarbon source may be pure carbon, char, biochar, charcoal, coal,biomass, or any other carbonaceous material.

In some embodiments, the process further comprises transporting at leasta portion of the carbon to an oxidation reactor. In certain embodiments,all of the carbon is transported to the oxidation reactor. The carbonmay be transported by a transporting means selected from the groupconsisting of truck, train, ship, barge, pipeline, bulk solids conveyer,and combinations thereof. A bulk solids conveyer may be any knownmaterial handling system, such as belt, screw or pneumatic conveyingsystems, for example.

In some particular embodiments, the carbon is transported by forming aslurry of carbon in liquid oxygen. The liquid oxygen may be derived fromreduction of the carbon oxide to the carbon. Because the slurry is at alow temperature, the combustion potential should be low. In theseembodiments, the carbon-oxygen slurry may be fed to an oxidationreactor, to generate energy and carbon oxide.

In some embodiments, the process further comprises intermediate storageof the carbon. The intermediate storage of the carbon may be located ata site associated with the energy as available, a site associated withthe energy on demand, or both of these. In some embodiments, the energyas available sub-system is co-located with the energy on demandsub-system, in which case the carbon intermediate storage may be at suchsingle site. Any other location may be used for intermediate storage ofthe carbon, if desired.

In some embodiments, the intermediate storage of the carbon may usepiles, rail cars, truck trailers, tanks, silos, bins, hoppers,intermediate bulk containers, sacks, drums and/or combinations thereof.

Some embodiments do not physically transport carbon to another location.For example, a common reactor may be utilized to reduce the carbon oxideto the carbon and then later to oxidize the carbon (or a portionthereof) to carbon oxide.

In preferred embodiments, the carbon is oxidized with anoxygen-containing compound as oxidant. The carbon may be oxidized withoxygen, which may be obtained from air and/or from the reduction of thecarbon oxide to carbon and oxygen. Alternatively, or additionally, thecarbon may be oxidized with a metal oxide or another oxygen-containingmetal species.

Some embodiments further comprise transporting the oxidant from areduction reactor to an oxidation reactor. Optionally, intermediatestorage of the oxidant is included, such as at a site associated withthe energy as available, or at a site associated with the energy ondemand, or both of these.

In some embodiments, the intermediate storage of the oxidant is locatedat a storage site that is not co-located with sites associated with theenergy as available or the energy on demand. For example, storage sitesfor the oxidant may be selected from the group consisting of an offsitestorage vessel, a pipeline, a gas distribution network (when the oxidantis a gas), the atmosphere (when the oxidant is O₂ or air), andcombinations thereof.

In some embodiments, the intermediate storage of the oxidant may usepiles, rail cars, truck trailers, tanks, silos, bins, hoppers,intermediate bulk containers, sacks, drums and/or combinations thereof.

The oxidation of the carbon will typically (although not necessarily) becarried out in an oxidation reactor operated at effective oxidationconditions to generate reaction energy and an oxidized stream comprisingthe consequent carbon oxide. Exemplary oxidation reactors include, butare not limited to, a boiler, a conventional coal-fired power plant, amodified coal-fired power plant, a non-catalytic combustion unit, acatalytic oxidation reactor, a chemical-looping combustion unit, a fuelcell, and an integrated gasification combined cycle unit. In someembodiments, the oxidation reactor is a molten carbonate fuel cell orsolid oxide fuel cell.

CN201865710U to Wu, et al., which is hereby incorporated by referenceherein, discloses a chemical-looping combustion system using a Nicatalyst that consumes coal and air, producing energy, essentially pureCO₂, H₂O, N₂, and slag. Coal is gasified into CO and CH₄, which is fedinto the first vessel where Ni is reduced. The nickel is oxidized in asecond vessel with air, to form nickel oxide. In embodiments of thisinvention, a feed of pure carbon could be gasified with CO₂ to generateCO as feed to a Ni reduction vessel, in which case the system would notgenerate H₂O.

Some or all of the carbon may be oxidized to generate the energy ondemand and the consequent carbon oxide. The reaction energy may bedirectly recovered as the energy on demand. Alternatively, oradditionally, the reaction energy may be converted to the energy ondemand. The energy on demand may be selected from the group consistingof electrical energy, mechanical energy, thermal energy, chemicalenergy, electromagnetic energy, and combinations thereof. In preferredembodiments, the energy on demand is dispatchable and distributablerenewable energy.

Preferably, at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, or 85% of thecarbon oxide is provided by recycling and/or reusing the consequentcarbon oxide. More preferably, at least 90%, 91%, 92%, 93%, 94%, 95%,96%, 97%, 98%, or 99% of the carbon oxide is provided by recyclingand/or reusing the consequent carbon oxide. Most preferably, all (oressentially all) of the carbon oxide is provided by the recycling and/orreusing the consequent carbon oxide. Any of these embodiments may beachieved in actuality or virtually.

In addition, in certain embodiments, essentially all (except for processlosses) of the consequent carbon oxide is recycled and/or reused. Notethat these embodiments are not necessarily the same as embodiments inwhich all of the carbon oxide is provided by the recycling and/orreusing of the consequent carbon oxide; in the former, consequent CO_(x)from oxidation is all recycled and/or reused, while in the latter, somefraction of consequent CO_(x) might not be recycled but all of thecarbon oxide for reduction is derived from recycle and/or reuse. Manyscenarios are possible due to transient versus steady-state operations,process losses and make-up streams, and recycling and/or reusing inactuality or virtually.

The consequent carbon oxide may be recycled and/or reused in actuality.Alternatively, or additionally, the consequent carbon oxide may berecycled and/or reused virtually via the atmosphere. Any combination orratio of carbon oxide recycled or reused actually, versus that recycledor reused virtually, may be employed. For example, the percentage ofcarbon oxide recycled or reused in actuality may be zero, or about 5%,10%, 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%.

In some embodiments, the process further comprises intermediate storageof the consequent carbon oxide. The intermediate storage of theconsequent carbon oxide may be located at a site associated with theenergy on demand and/or at a site associated with the energy asavailable. In some embodiments, the intermediate storage of theconsequent carbon oxide is located at a carbon oxide storage site thatis not co-located with sites associated with the energy as available orthe energy on demand. For example, the carbon oxide storage site may beselected from the group consisting of an offsite storage vessel, apipeline, a gas distribution network, an underground geologicalformation, a body of water, the atmosphere, and combinations thereof.

In some embodiments, the intermediate storage of the carbon oxide mayuse rail cars, truck trailers, tanks, silos, bins, hoppers, intermediatebulk containers, sacks, drums and/or combinations thereof.

The energy as available sub-system may be co-located with the energy ondemand sub-system at a single plant site. Or, the energy as availablesub-system and the energy on demand sub-system may be located atseparate sites.

In preferred embodiments of the invention, the process generatesessentially no net carbon emissions (as carbon oxide). Again, theattainment of no net carbon may be achieved in actuality or virtually.

Variations of this invention involve a number of process steps, many ofwhich are optional. The steps may involve multiple sub-steps. It shouldbe noted that the steps may involve additional input and output streamsnot shown or described.

Referring now generally to FIGS. 1-5, block flow diagrams of exemplaryembodiments of the present disclosure are illustrated. It should beappreciated that these figures represent some example embodiments butnot all contemplated embodiments of the present disclosure. As discussedbelow, various additional non-illustrated embodiments and combinationsof the several components and features discussed herein are alsocontemplated.

FIGS. 1-5 present process block flow diagrams of some embodiments of theinvention. The diagrams use circles for inputs and outputs, rectanglesfor process steps, lines with arrows to show the flow of material andenergy, and rounded rectangles for material sources and sinks Items thatare optional are denoted with dashed lines. Alternating dot-dashed linesencompass items preferably in the vicinity of each other, in sub-systemsdenoted as “energy as available” and “energy on demand” (in FIG. 2).

In FIG. 1, the energy source may be any form of energy, generally aprimary energy source. The energy source is preferably a renewableenergy source. “Secondary energy” is an optional form of energygenerated from the energy source. Secondary energy is generally thermalor electrical energy, but may be other forms of energy.

The “convert source energy” step converts an energy source intosecondary energy and, optionally, generates carbon oxide. The preferredform of secondary energy is generally electricity, although heat may bedesirable when the energy source is solar or geothermal energy.

The “reduce carbon oxide” step of FIG. 1 uses the energy source and/orsecondary energy to chemically reduce carbon oxide to carbon and oxygen.Carbon oxide may be either carbon monoxide, carbon dioxide, or a mixtureof both. Carbon oxide may be carbon dioxide extracted from air, fluegases, or other sources.

The carbon oxide reduction, as discussed above, may be accomplished byvarious means known in the art. The carbon oxide reduction may involveelectrons, negative ions, plasma, photons, or metal/metal oxides, forexample. In some embodiments, the carbon oxide reduction does notinvolve hydrogen (H₂) or hydrogen-containing compounds, including water.

The overall chemical reaction for this step, summarizing the result ofchemical reactions of all sub-steps within this step, is:CO_(x)+energy→C+0.5xO₂This step also may include the sub-step of separating carbon and oxygen(or another oxidant) and may include other upstream and downstreamprocess steps as required by the particular embodiment of the invention.

In particular, sub-steps of this step may include water as a reactantand/or product, such as according to the equations:nH₂O→nH₂+(0.5n)O₂CO_(x) +nH₂→C+nH₂OThe net result of these reactions is the reduction of carbon oxide tocarbon and oxygen. In general, this invention shall not be limited byany particular reaction mechanisms that take place to achieve theoverall chemistry.

U.S. Pat. No. 3,861,885 to Schora, which is incorporated by referenceherein, describes a process for producing nonpolluting carbon black fuelfrom polluting carbonaceous fossil fuels. The carbon deposition step ofthe Schora process involves producing carbon black from a carbonmonoxide rich gas stream generated by gasification of fossil fuel. Insome embodiments, the present invention uses the carbon deposition stepof Schora as part of the carbon oxide reduction step.

In other embodiments of the present invention that use carbon dioxide,rather than carbon monoxide, as the input to the “reduce carbon oxide”step, carbon dioxide is first converted to carbon monoxide either usinghydrogen produced from the electrolysis of water via equation to effectthe water-gas shift reaction,CO₂+H₂→CO+H₂Oand/or using some recycled carbon according to the reverse Boudouardreaction:C+CO₂→2CO

U.S. Pat. No. 6,270,731 to Kato, et al., which is incorporated byreference herein, discloses a carbon fixation reactor operatingaccording to the equation:CO₂+2H₂→C+2H₂OHydrogen for this process could be produced by cleaving water withenergy as available or secondary energy, such as by electrolysis:2H₂O→2H₂+O₂

U.S. Patent Application Publication Nos. 20090013593A1 and20090016948A1, both to Young and each incorporated by reference herein,teach methods for reducing carbon dioxide produced from carbonaceousfuel using various combinations of magnesium, magnesium oxides, andmagnesium salts. In these applications of Young, CO₂ is introduced ontoan electrode with an applied voltage to form Mg from MgO. The Mg reactswith CO₂ to form CO and carbon, and MgO. The reaction is driven tocompletion by a constant gas pressure, and the carbon layer can beharvested. The carbon may be washed to recover residual oxide and salts.In some embodiments of the present invention, the methods of Young areused as part of the “reduce carbon oxide” step.

The “oxidize carbon” step in FIG. 1 chemically oxidizes carbon usingoxidant producing carbon oxide and energy of reaction. The oxidant maybe provided by air, pure oxygen, oxygen-enriched air or metal oxide. Theblock for this step includes the overall chemical reaction, summarizingthe result of chemical reactions of all sub-steps in this step, isC+0.5xO₂→CO_(x)+energyOxidizing carbon may be done by combustion, generating heat; or in afuel cell, generating primarily electricity. It may include the sub-stepof separating carbon oxide from the reactants and may include otherupstream and downstream process steps as required by the particularembodiment of the invention.

In FIG. 1, the “atmosphere” is the blanket of air covering the earth. Itis a source and sink for atmospheric gases, namely oxygen and carbondioxide, pertinent to some embodiments of the invention. Because theatmosphere is in nearly constant motion and its constituents can beextracted from or exhausted to it anywhere on earth, the atmosphere mayfunction as a virtual storage and transport system for oxygen and carbondioxide.

The block flow diagram of FIG. 2 designates two sub-systems, “energy asavailable” and “energy on demand.” “Energy as available” is the locationof the energy source and the carbon oxide reduction step, which producescarbon. “Energy on demand” is the location of the carbon oxidation stepand the “convert produced energy” step, required for some embodiments ofthe invention, to generate useful energy. Although the two locationscould be co-located, they may be distant from each other and arepotentially hundreds or even thousands of miles apart.

The “store produced carbon oxide” step involves storing carbon oxideproduced from the “oxidize carbon” step. The “transport carbon oxide”step involves transporting carbon oxide from the vicinity of the “energyon demand” sub-system to the vicinity of the “energy as available”sub-system. The “store carbon oxide for use step” involves storingcarbon oxide for future use in the vicinity of the “energy as available”sub-system. All of these steps are optional.

The “store produced carbon” step involves storing carbon produced fromthe “reduce carbon oxide” step for future transport. The “transportcarbon” step involves transporting carbon from the vicinity of the“energy as available” sub-system to the vicinity of the “energy ondemand” sub-system. The “store carbon for use” step involves storingcarbon for future use in the vicinity of the “energy on demand”sub-system. All of these steps are optional.

The “store produced oxygen” step involves storing oxygen produced fromthe “reduce carbon oxide” step for future transport. The “transportoxygen” step involves transporting oxygen from the vicinity of the“energy as available” sub-system to the vicinity of the “energy ondemand” sub-system. The “store oxygen for use” step involves storingoxygen for future use in the vicinity of the carbon oxidation step. Allof these steps are optional.

In some embodiments of the invention relating to FIG. 2, renewableenergy at the location of “energy as available” is converted toelectricity when the renewable energy is available. As electricity isgenerated, it is used to chemically reduce carbon dioxide, stored at thelocation of “energy as available,” to carbon and oxygen. The carbon,essentially captured renewable energy, is stored in the vicinity of the“energy as available” until it is transported to the vicinity of “energyon demand,” where it is stored for use in the carbon oxidation step. Asuseful energy is needed, such as in response to a dynamic demand forenergy, the stored carbon may be oxidized using air from the atmosphereor transported oxygen (from the carbon oxide reduction). Oxygen oxidizesthe carbon, releasing carbon oxide and the energy of reaction, such asheat, which may be converted to electricity as the preferred form ofuseful energy, by means well-understood by one skilled in the art. Inprinciple, the oxygen from the atmosphere could be purified oxygen fromair, or oxygen-enriched air.

FIG. 3 is a process block-flow diagram depicting some embodiments of theinvention utilizing supplemental carbon, to transform energy asavailable to energy on demand. The FIG. 3 diagram uses circles forinputs and outputs, rectangles for process steps, lines with arrows toshow the flow of material and energy, and rounded rectangles formaterial sources and sinks. Items that are optional are denoted withdashed lines. In FIG. 3, the energy source may be any form of energy,generally a primary energy source. The energy source is preferably arenewable energy source. “Secondary energy” is an optional form ofenergy generated from the energy source. Secondary energy is generallythermal or electrical energy, but may be other forms of energy.

FIG. 4 is a process block-flow diagram depicting some embodiments of theinvention utilizing metals and metal oxides, to transform energy asavailable to energy on demand. The FIG. 4 diagram uses circles forinputs and outputs, rectangles for process steps, lines with arrows toshow the flow of material and energy, and rounded rectangles formaterial sources and sinks Items that are optional are denoted withdashed lines. In FIG. 4, the energy source may be any form of energy,generally a primary energy source. The energy source is preferably arenewable energy source.

FIG. 5 is a process block-flow diagram depicting some embodiments of theinvention utilizing supplemental carbon oxide, to transform energy asavailable to energy on demand. The FIG. 5 diagram uses circles forinputs and outputs, rectangles for process steps, lines with arrows toshow the flow of material and energy, and rounded rectangles formaterial sources and sinks Items that are optional are denoted withdashed lines. In FIG. 5, the energy source may be any form of energy,generally a primary energy source. The energy source is preferably arenewable energy source. “Secondary energy” is an optional form ofenergy generated from the energy source. Secondary energy is generallythermal or electrical energy, but may be other forms of energy.

In some embodiments of the invention, the “energy on demand” location isa coal-fired power plant. The invention may virtually eliminate airpollution from coal-fired power plants while improving the utilizationof both renewable energy resources and coal-fired power plants.

In some embodiments of the invention, the carbon oxide produced byoxidation is liquefied and stored at the location of “energy on demand”until it is transported to the location of “energy as available.” As thestored carbon oxide is used in the carbon oxide reduction step, thecycle starts over again. In some embodiments of the invention,containers used for transporting carbon can also be used fortransporting liquid carbon oxide, thereby increasing their utilizationand decreasing the incremental cost of transporting liquid carbon oxide.

In some embodiments of the invention, the net effect of this process isthat renewable energy, for which the available location, time, and ratecannot be controlled, is rendered dispatchable, being converted toelectricity on demand at the location, time and rate needed. Thematerials used in the process are either virtually recycled via theatmosphere or actually recycled by transporting them between thelocations of “energy as available” and “energy on demand.” Therefore,the process preferably generates virtually no air pollutants or netcarbon dioxide. Air pollutants may arise from transportation ofmaterials. By “no net carbon dioxide” emissions, and the like, it ismeant and understood that carbon dioxide losses in the process areinevitable in actual practice.

There are many embodiments, variations, and permutations of thisinvention, as will be recognized by one skilled in the art or skilled inchemical engineering.

In some embodiments, the energy source is used directly withoutconversion to chemically reduce carbon, such as by a photocatalyticreaction, which uses photons from sunlight, i.e. solar energy. In someembodiments, the energy source is converted to heat, rather thanelectricity, for the carbon oxide reduction step.

In some embodiments, the energy source is fossil fuel or, preferably,biomass and is oxidized in the “convert source energy” step, producingenergy for the “reduce carbon oxide” step. In these embodiments, the“convert source energy” step also generates carbon oxide, which can beused to replace some or all of the carbon and/or some or all of thecarbon oxide lost from the process.

In some embodiments, the carbon oxide reduction step uses carbon dioxidefrom air, rather than stored carbon oxide. This eliminates the need totransport carbon oxide from the location of energy on demand to thelocation of energy as available. Carbon dioxide may be recovereddirectly from the atmosphere by separation means and/or reaction means,as described previously.

Carbon may be transported by whatever means is available, includingtruck, train, or, perhaps, pipeline (as a slurry). The preferable modeof transportation will depend on the locations of energy as availableand energy on demand and availability of the various modes oftransportation between locations. If available, train is generallypreferred because it has lower energy intensity than truck and issimpler than pipeline, which would likely require slurried carbon. It ispossible to create a slurry of carbon in liquid oxygen, in which carbonand oxygen can be transported and, possibly, stored together.

The oxidation step using pure oxygen, rather than air, would providemore usable energy and fewer impurities because the nitrogen in airgenerally reduces the available energy of reaction and can react to formundesirable byproducts. However, transporting the oxygen, rather thanusing air from the atmosphere, requires more energy and greater capitalcost for transportation. Preferred configurations meet regulatory andoperating requirements with the lowest total cost. In general, some airwill be necessary to replace oxygen lost in storage and transportation.

In some embodiments, energy as available and energy on demand areco-located, so that neither carbon, oxygen, nor carbon oxide aretransported, but are stored on location. In this instance, the inventioncan be used to provide base load leveling for a modified coal-firedpower plant. No renewable energy is required, but the invention mayincrease the utilization of the coal-fired power plant.

In some embodiments, the “oxidize carbon” step is accomplished in a fuelcell, preferably a molten carbonate or solid oxide fuel cell, in whichcase the energy of reaction is primarily electricity. In theseembodiments, the “convert produced energy” step may not be necessary.

In some embodiments, at or near a renewable energy source, generatedenergy may be used to produce carbon from carbon oxide according to theoverall reaction equation:CO_(x)+M+energy→C+MO_(x)where M=metal/metal oxide. This reaction is endothermic reduction ofcarbon oxide to carbon using a metal/metal oxide M as a reductant, withoxidation of metal/metal oxide to a metal oxide (MO_(x)) with a higheroxidation state.

At the site of energy on demand, the carbon is oxidized with the metaloxide (from the reduction) as oxidant, to produce carbon oxide,according to the overall reaction equation:C+MO_(x)→CO_(x)+M+energyThis reaction is exothermic oxidation of carbon to produce carbon oxide,with reduction of metal oxide to a metal or metal oxide of a loweroxidation state. The metal/metal oxide may then be reused as areductant.

The metal/metal oxide M may be or contain an alkali earth metal, analkaline earth metal, a transition metal, or oxides thereof, forexample. The metal/metal oxide M may be selected from the groupconsisting of iron, nickel, cobalt, molybdenum, copper, zinc, manganese,vanadium, and combinations or oxides thereof.

For example, Ehrensberger, et al., “Production of Carbon from CarbonDioxide with Iron Oxides and High-Temperature Solar Energy” Ind. Eng.Chem. Res. 1997, 36, 645-648, which is incorporated by reference, it wasdemonstrated that CO₂ can be thermally reduced to carbon withconcentrated solar energy, to drive reactions between CO₂ and ironoxides. Iron oxides are capable of splitting CO₂ into C and O₂. In thiscase, the oxidant is actually a metal oxide, not a metal, but it isreduced to a metal oxide having an even higher oxidation state.

A closed reactor is not necessary for the present invention, in certainembodiments. For example, the carbon oxide reduction step could beperformed with a large array of metal/metal oxide surfaces, optionallyconfigured with solar input means, so that carbon dioxide is extracteddirectly from the atmosphere to form carbon and metal oxide. When solarinput means are also included, the electricity may drive the carbonoxide reduction, but other energy input may be included. The array thenbecomes one of metal oxide and carbon, either or both of which may beseparated. The reverse may then later be carried out, to oxidize carbonand metal oxide to metal/metal oxide and carbon oxide, producing energywhich could utilize a portion of the same solar input means as energyoutput means. Other types of open reactors are possible.

Some embodiments of the invention provide a process for producing energyon demand, the process comprising:

-   -   (a) obtaining carbon oxide;    -   (b) obtaining a source of available energy;    -   (c) converting the carbon oxide, in a first reactor operated at        effective reduction conditions using the available energy, to a        reduced stream comprising carbon and oxygen;    -   (d) transporting at least a portion of the carbon to a second        reactor, with optional intermediate storage of the carbon prior        to step (f);    -   (e) optionally transporting at least a portion of the oxygen to        the second reactor, separately from the carbon, and with        optional intermediate storage of the oxygen prior to step (f);    -   (f) in response to a demand for energy, oxidizing at least a        portion of the carbon with an oxidant, in the second reactor        operated at effective oxidation conditions to generate reaction        energy and an oxidized stream comprising produced carbon oxide;    -   (g) recovering the reaction energy as, and/or converting the        reaction energy to, useful energy to satisfy the demand for        energy; and    -   (h) recycling at least some of the produced carbon oxide to        step (c) to convert at least some of the produced carbon oxide,        in the first reactor operated at effective reduction conditions,        to the reduced stream comprising the carbon and the oxygen.

Some embodiments of the invention provide a process for producing energyon demand, the process comprising:

-   -   (a) obtaining carbon dioxide;    -   (b) obtaining a source of available energy;    -   (c) converting the carbon dioxide, in a first reactor operated        at effective reduction conditions using the available energy, to        a reduced stream comprising carbon and oxygen;    -   (d) transporting at least a portion of the carbon to a second        reactor, with optional intermediate storage of the carbon prior        to step (f);    -   (e) optionally transporting at least a portion of the oxygen to        the second reactor, separately from the carbon, and with        optional intermediate storage of the oxygen prior to step (f);    -   (f) in response to a demand for energy, oxidizing the at least a        portion of the carbon with an oxidant, in the second reactor        operated at effective oxidation conditions to generate reaction        energy and an oxidized stream comprising produced carbon        dioxide;    -   (g) recovering the reaction energy as, and/or converting the        reaction energy to, useful energy to satisfy the demand for        energy; and    -   (h) virtually recycling at least some of the produced carbon        dioxide to step (c) by the substeps of: (1) discharging at least        some of the produced carbon dioxide to the atmosphere; (2)        tracking the quantity of discharged carbon dioxide; (3)        obtaining an equivalent amount of carbon dioxide directly from        the atmosphere or indirectly from a source (e.g., from biomass        or coal combustion) that would otherwise be emitted to the        atmosphere; and (4) introducing the equivalent amount of carbon        dioxide to step (c) such that during step (h), no net carbon        dioxide is emitted to the atmosphere.

In some embodiments, carbon sequestration may be utilized for a portionof the carbon produced by carbon oxide reduction. In these embodiments,credits (through various market or regulatory mechanisms) may beobtained, and such credits may be applied so that essentially no netcarbon is emitted to the atmosphere or carbon is effectively removedfrom the atmosphere.

Some embodiments of the invention provide a system for producing energyon demand from available energy, the system comprising:

-   -   (a) a source of available energy;    -   (b) a first reactor, in operable communication with the        available energy, capable of converting carbon oxide to a        reduced stream comprising carbon and oxygen;    -   (c) a second reactor capable of oxidizing the carbon to generate        reaction energy and an oxidized stream comprising produced        carbon oxide;    -   (d) a carbon transporting means to convey the carbon from the        first reactor to the second reactor;    -   (e) an optional oxygen transporting means to convey the oxygen        from the first reactor to the second reactor;    -   (f) a carbon oxide transporting means to recycle the produced        carbon oxide to the first reactor; and    -   (g) an energy recovery means to recover the reaction energy as,        and/or convert the reaction energy to, useful energy to satisfy        an external demand for energy.

Some embodiments of the invention provide a system for producing energyon demand from available energy, the system comprising:

-   -   a first reactor that converts carbon oxide to carbon and oxygen,        wherein the first reactor utilizes available energy;    -   a second reactor that oxidizes the carbon with an oxidant to        generate useful energy on demand, wherein the oxidant optionally        includes the oxygen;    -   a physical carbon management subsystem for conveying the carbon        from the first reactor to the second reactor;    -   a physical or virtual oxygen management subsystem for conveying        the oxygen from the first reactor to the second reactor; and    -   a physical or virtual carbon oxide management subsystem for        recycling the carbon oxide from the second reactor to the first        reactor.

Some embodiments of the invention provide a process for producing energyon demand from available energy, the method comprising:

-   -   in a first reactor, converting carbon oxide to carbon and        oxygen, wherein the first reactor utilizes available energy;    -   in a second reactor, oxidizing the carbon with an oxidant to        generate useful energy on demand, wherein the oxidant optionally        includes the oxygen;    -   physically conveying the carbon from the first reactor to the        second reactor;    -   physically or virtually conveying the oxygen from the first        reactor to the second reactor; and    -   physically or virtually recycling the carbon oxide from the        second reactor to the first reactor.

Commercially available apparatus and equipment, known to one of skill inthe art, may be employed for the processes of the invention.

The carbon oxide reduction and carbon oxidation steps are typicallycarried out in reactors. As will be understood, any of the reactorsdiscussed herein can be independent reactors, or alternatively a singlereactor can include a plurality of zones, or a combination thereof.

When a single reactor is employed, multiple zones can be present.Multiple zones, such as two, three, four, or more zones, can allow forthe separate control of temperature, solids residence time, gasresidence time, gas composition, flow pattern, and/or pressure in orderto adjust the overall process performance.

References to “zones” shall be broadly construed to include regions ofspace within a single physical unit, physically separate units, or anycombination thereof. For example, the demarcation of zones within areactor may relate to structure, such as the presence of flights ordistinct heating elements to provide heat to separate zones.Alternatively, or additionally, in various embodiments, the demarcationof zones may relate to function, such as distinct temperatures, fluidflow patterns, solid flow patterns, and extent of reaction. It will beappreciated that there are not necessarily abrupt transitions from onezone to another zone. In a single batch reactor, “zones” are operatingregimes in time, rather than in space. Various embodiments include theuse of multiple batch reactions.

Some embodiments promote additional carbon formation by including aseparate unit or zone in which cooled carbon is subjected to anenvironment including carbon-containing species, such as supplementalcarbon, to increase the quantity of carbon.

There are a large number of options as to intermediate input and outputstreams of one or more phases present in any particular reactor, variousmass and energy recycle schemes, various additives that may beintroduced anywhere in the process, adjustability of process conditionsincluding both reaction and separation conditions in order to tailorproduct distributions, and so on. Zone or reactor-specific input andoutput streams enable good process monitoring and control, such asthrough FTIR sampling and dynamic process adjustments.

In various embodiments, chemical reactions continue to occur in acooling zone. It should be appreciated that in various embodiments, somereactions are actually initiated in the cooling zone. For example, thecooling zone may be a “carbon collection zone” in which carbon is formedand/or collected following formation. Carbon-containing components thatare in the gas phase can condense (due to the reduced temperature of thecooling zone). The temperature remains sufficiently high, however, topromote reactions that may form additional carbon. One exemplaryreaction that may take place is the conversion of carbon monoxide tocarbon dioxide plus fixed carbon (Boudouard reaction), discussed above.

The residence times of the zones may vary. For a desired amount ofreaction, higher temperatures may allow for lower reaction times, andvice versa. The residence time in a continuous reactor is the volumedivided by the volumetric flow rate. The residence time in a batchreactor is the batch reaction time, following heating to reactiontemperature.

It should be recognized that in multiphase reactor, there are multipleresidence times. In the present context, in each zone, there will be aresidence time (and residence-time distribution) of both the solidscarbon-rich phase and the vapor phase.

The solids residence time may be selected from about 1 millisecond toabout 4 hours, depending on the temperature and time desired. Theheat-transfer rate, which will depend on the particle or gas type, thephysical apparatus, and the heating parameters, will dictate the minimumresidence time necessary to allow the solids to reach a predeterminedpreheat temperature.

The temperature within the reduction reactor may be selected from about−60° C. to about 2,400° C., such as about 31° C.

Depending on the temperature in the reduction reactor, there should besufficient time to allow the carbon-forming chemistry to take place,following the necessary heat transfer. For short times, the temperaturewould need to be quite high and could promote generation of vapors andgases derived from the carbon itself, which is to be avoided when theintended intermediate product is solid carbon.

As discussed above, the residence time of the vapor phase may beseparately selected and controlled. The vapor residence time of thereactor may be selected from about 1 millisecond to about 1 hour. Shortvapor residence times promote fast sweeping of volatiles out of thesystem, while longer vapor residence times promote reactions ofcomponents in the vapor phase with the solid phase.

The mode of operation for any reactor, and overall system, may becontinuous, semi-continuous, batch, or any combination or variation ofthese. In some embodiments, a reactor is a continuous, countercurrentreactor in which reactants and products flow substantially in oppositedirections. A reactor may also be operated in batch but with simulatedcountercurrent flow of vapors, such as by periodically introducing andremoving gas phases from the batch vessel.

Also, as discussed previously, a single common reactor may be utilizedboth for carbon oxide reduction, and then later for carbon oxidation. Insuch embodiments, typically there will be removal of the oxygen oroxygen-containing species from the reactor, following the reductionreaction. Then, when energy of reaction is desired, an oxidant (whichmay be the same oxygen or oxygen-containing species that was removedpreviously, or another oxidant) is introduced to cause combustion orcatalytic oxidation, for example. In embodiments in which carbon oxideis reduced with a metal/metal oxide to a metal oxide, it would bepossible to remove the carbon product from the reactor, and leave behindthe metal oxide. Then when reaction energy is desired, carbon (the sameor different carbon) may be introduced for oxidation with the metaloxide to form metal/metal oxide, carbon oxide, and energy.

Various flow patterns may be desired or observed. With chemicalreactions and simultaneous separations involving multiple phases inmultiple zones, the fluid dynamics can be quite complex. Typically, theflow of solids may approach plug flow (well-mixed in the radialdimension) while the flow of vapor may approach fully mixed flow (fasttransport in both radial and axial dimensions). Multiple inlet andoutlet ports for vapor may contribute to overall mixing.

The pressure in each reactor or zone may be separately selected andcontrolled. The pressure of each zone may be independently selected fromabout 1 kPa to about 10⁴ kPa, such as about 7,480 kPa. Independent zonecontrol of pressure is possible when multiple gas inlets and outlets areused, including vacuum ports to withdraw gas when a zone pressure lessthan atmospheric is desired. Similarly, in a multiple reactor system,the pressure in each reactor may be independently selected andcontrolled.

A substantially inert sweep gas may be introduced into one or more ofreactors or zones. Product gases are then carried away from the zone(s)in the sweep gas, and out of the reactor. The sweep gas may be N₂, Ar,He, air, or combinations thereof, for example. The sweep gas may firstbe preheated prior to introduction, or possibly cooled if it is obtainedfrom a heated source.

In certain embodiments, the sweep gas in conjunction with a relativelylow process pressure, such as atmospheric pressure, provides for fastvapor removal without large amounts of inert gas necessary. In someembodiments, the sweep gas flows countercurrent to the flow direction offeedstock. In other embodiments, the sweep gas flows cocurrent to theflow direction of feedstock. In some embodiments, the flow pattern ofsolids approaches plug flow while the flow pattern of the sweep gas, andgas phase generally, approaches fully mixed flow in one or more zones.

In some embodiments, the zone or zones in which separation is carriedout is a physically separate unit from the reactor. The separation unitor zone may be disposed between zones, if desired. For example, theremay be a separation unit placed between reactors.

The sweep gas may be introduced continuously, especially when the outputsolids flow is continuous. When the reaction is operated as a batchprocess, the sweep gas may be introduced after a certain amount of time,or periodically, to remove gases. Even when the reaction is operatedcontinuously, the sweep gas may be introduced semi-continuously orperiodically, if desired, with suitable valves and controls.

The yield of carbon from carbon oxide may vary, depending on theabove-described factors including type of feedstock and processconditions. In some embodiments, the net conversion of starting CO_(x)to carbon is at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%,99% or higher.

Various additives may be introduced throughout the process, before,during, or after any step disclosed herein. The additives may be broadlyclassified as process additives, selected to improve process performancesuch as carbon yield or time/temperature to achieve a desired carbonyield. The additive may be added at any suitable time during the entireprocess.

Additives may be incorporated at supply facilities, transport trucks,unloading equipment, storage bins, conveyors (including open or closedconveyors), dryers, process heaters, or any other units. Additives maybe added anywhere into the process itself, using suitable means forintroducing additives.

In some embodiments, an additive is selected from a metal, a metaloxide, a metal hydroxide, or a combination thereof. In some embodiments,an additive is selected from an acid, a base, or a salt thereof.

The additives may be applied as a solid powder, a spray, a mist, aliquid, or a vapor. In some embodiments, additives may be introducedthrough spraying of a liquid solution (such as an aqueous solution or ina solvent), or by soaking in tanks, bins, bags, or other containers.

In some embodiments, a separating step comprises filtration, which mayfor example utilize fabric filters. In some embodiments, separatingcomprises electrostatic precipitation. In other embodiments, magneticseparation may be used. Scrubbing (including wet or dry scrubbing) mayalso be employed.

The throughput, or process capacity, may vary widely from smalllaboratory-scale units to full commercial-scale operations, includingany pilot, demonstration, or semi-commercial scale. In variousembodiments, the process capacity is at least about 1 kg/day, 10 kg/day,100 kg/day, 1 ton/day (all tons are metric tons), 10 tons/day, 100tons/day, 500 tons/day, 1000 tons/day, 2000 tons/day, or higher.

Solid, liquid, and gas streams produced or existing within the processcan be independently recycled, passed to subsequent steps, orremoved/purged from the process at any point.

The system may include a purging means for removing oxygen from thesystem. For example, the purging means may comprise one or more inletsto introduce a substantially inert gas, and one or more outlets toremove the substantially inert gas and displaced oxygen from the system.In some embodiments, the purging means is a deaerater disposed inoperable communication with the reduction reactor.

Gas inlets and outlets allow not only introduction and withdrawal ofvapor, but gas outlets (probes) in particular allow precise processmonitoring and control across various stages of the process. Preciseprocess monitoring would be expected to result in yield and efficiencyimprovements, both dynamically as well as over a period of time whenoperational history can be utilized to adjust process conditions.

In some embodiments, a reaction gas probe is disposed in operablecommunication with a reactor. Such a reaction gas probe may be useful toextract gases and analyze them, in order to determine extent ofreaction, selectivity, or other process monitoring. Then, based on themeasurement, the process may be controlled or adjusted in any number ofways, such as by adjusting feed rate, rate of inert gas sweep,temperature (of one or more zones), pressure (of one or more zones), andso on.

As intended herein, monitor and control includes any one or more sampleextractions via reaction gas probes, and optionally making process orequipment adjustments based on the measurements, if deemed necessary ordesirable, using well-known principles of process control (feedback,feedforward, proportional-integral-derivative logic, etc.).

The reactor or reactors may be selected from any suitable reactorconfiguration that is capable of carrying out the process. Exemplaryreactor configurations include, but are not limited to, fixed-bedreactors, fluidized-bed reactors, entrained-flow reactors, augers,rotating cones, rotary drum kilns, moving-bed reactors, or transport-bedreactors. Continuous reactors may be well-mixed or plug-flow, orsomething between these extremes.

The overall system may be at a fixed location, or it may be madeportable. The system may be constructed using modules which may besimply duplicated for practical scale-up. The system may also beconstructed using economy-of-scale principles, as is well-known in theprocess industries.

Separation techniques can include or use distillation columns, flashvessels, centrifuges, cyclones, membranes, filters, packed beds,capillary columns, and so on. Separation can be principally based, forexample, on distillation, absorption, adsorption, or diffusion, and canutilize differences in vapor pressure, chemical activity, molecularweight, density, viscosity, polarity, chemical functionality, affinityto a stationary phase, and any combinations thereof.

Separation of carbon may include filtration (e.g., fabric filters) orelectrostatic precipitation (ESP), for example. Fabric filters, alsoknown as baghouses, may utilize engineered fabric filter tubes,envelopes, or cartridges, for example. There are several types ofbaghouses, including pulse-jet, shaker-style, and reverse-air systems.The separation may also include scrubbing.

An electrostatic precipitator, or electrostatic air cleaner, is aparticulate collection device that removes particles from a flowing gasusing the force of an induced electrostatic charge. Electrostaticprecipitators are highly efficient filtration devices that minimallyimpede the flow of gases through the device, and can easily remove fineparticulate matter from the air stream. An electrostatic precipitatorapplies energy only to the particulate matter being collected andtherefore is very efficient in its consumption of energy (electricity).

The electrostatic precipitator may be dry or wet. A wet electrostaticprecipitator operates with saturated gas streams to remove liquiddroplets such as sulfuric acid mist from industrial process gas streams.Wet electrostatic precipitators may be useful when the gases are high inmoisture content, contain combustible particulate, or have particlesthat are sticky in nature.

Carbon, hydrogen, and nitrogen may be measured using ASTM D5373 forultimate analysis, for example. Oxygen may be estimated using ASTMD3176, for example. Sulfur may be measured using ASTM D3177, forexample.

Certain embodiments provide carbon intermediate materials with little oressentially no hydrogen (except from any moisture that may be present),nitrogen, phosphorus, or sulfur, and are substantially carbon plus anymoisture present. Therefore, some embodiments provide a material with upto and including 100% carbon, on a dry/ash-free (DAF) basis, noting thatash if present would not be expected to derive from the CO_(x) but mayderive from the system itself or impurities that enter the system. Ashmay be measured using ASTM D3174, for example.

Various amounts of moisture may be present. On a total mass basis, thecarbon material may comprise at least 0.1 wt %, 0.5 wt %, 1 wt %, 2 wt%, 5 wt %, or more of moisture. As intended herein, “moisture” is to beconstrued as including any form of water present in the carbon product,including absorbed moisture, adsorbed water molecules, chemicalhydrates, and physical hydrates. The equilibrium moisture content mayvary at least with the local environment, such as the relative humidity.Also, moisture may vary during transportation, preparation for use, andother logistics. Moisture may be measured by any suitable method knownin the art, including ASTM D3173, for example.

The carbon material may have various “energy contents” which for presentpurposes means the energy density based on the higher heating valueassociated with total combustion of the bone-dry reagent. For example,the carbon may possess an energy content of about at least 12,000Btu/lb, at least 13,000 Btu/lb, or at least 14,000 Btu/lb. The energycontent may be measured by any suitable method known in the art,including ASTM D5865, for example.

The carbon material may be in the form of a powder, such as a coarsepowder or a fine powder. The carbon may be further pulverized to form afine powder. “Pulverization” in this context is meant to include anysizing, milling, pulverizing, grinding, crushing, extruding, or otherprimarily mechanical treatment to reduce the average particle size. Whenit is desired to increase bulk density, agglomeration, pelletizing, orcompression may be performed on the carbon powder, according to knownprinciples. The mechanical treatments to alter the carbon density may beassisted by chemical or electrical forces, if desired. Such treatmentsmay be batch, continuous, or semi-continuous and may be carried out at adifferent location than that of formation of the carbon solids, in someembodiments.

In some embodiments, the majority of carbon contained in the carbonmaterial is classified as renewable carbon. In some embodiments,substantially all of the carbon is classified as renewable carbon. Theremay be certain market mechanisms (e.g., Renewable IdentificationNumbers, carbon credits, etc.) wherein value is attributed to therenewable carbon content within the carbon material.

Variations of the present invention provide many advantages andfeatures. Some embodiments may realize high theoretical effective energydensity compared to alternative processes. Some embodiments may realizehigh theoretical effective specific energy. Some embodiments may produceand manage renewable energy that is easily and economically stored forlong periods of time, and is easily and economically transported.

Embodiments may utilize existing technology and infrastructure forproducing, storing, handling, transporting, and using carbon. Carbon isrelatively safe. Technology to control and mitigate chemical andbiological hazards exists and is widely practiced.

The process of some embodiments of the invention may be used inconjunction with a distributed generation electrical power system. Theprocess of the present invention may be carbon neutral and may beconfigured to generate little, if any, net carbon dioxide or chemicalpollution.

This invention is capable of converting and storing energy in a formthat makes it dispatchable, i.e. able to be transported to where it isneeded for use when it is needed. The energy carrier provided by theinvention is storable. That is, the invention makes practical thestorage and dispatch of energy sources that are either not storableand/or not transportable. The energy carrier provided by the inventionis practical and widely applicable, especially for electrical powergeneration. In preferred embodiments, the invention converts and storesrenewable energy—rendering renewable energy sources storable anddispatchable.

The utilization of renewable energy source may therefore be increased,by practicing the processes disclosed herein. Also, the invention candecrease the excess conventional electrical generation capacity requiredto utilize renewable energy sources while ensuring that electricalenergy demand is satisfied.

This invention can provide carbon-neutral energy, especially forelectrical power generation. This invention can provide a renewableenergy carrier that is minimally hazardous, i.e. relatively safe tohandle and non-toxic. The energy carrier is also recyclable. Thisinvention can minimize air pollution created by the generation and useenergy on demand, especially electricity.

In the U.S., nearly half of electricity is produced by burning coal,which is basically impure carbon. Therefore, utilizing carbon fromrenewable sources to generate electricity with existing power plantsshould require minimal changes to existing coal burning power plants.Carbon is already produced, handled, and used industrially in largequantities as carbon black, so the technology and infrastructure forstoring, handling and transporting carbon safely and efficiently exists.In addition, carbon has minimal health and safety issues.

Although it is not likely to displace fossil fuels for automobiles,carbon could be used as storable fuel for larger vehicles, such asbuses, trucks, trains and ships. In accordance with this invention,carbon can create a sustainable, carbon-neutral process to utilizerenewable energy for various applications.

In this detailed description, reference has been made to multipleembodiments of the invention and non-limiting examples relating to howthe invention can be understood and practiced. Other embodiments that donot provide all of the features and advantages set forth herein may beutilized, without departing from the spirit and scope of the presentinvention. This invention incorporates routine experimentation andoptimization of the methods and systems described herein. Suchmodifications and variations are considered to be within the scope ofthe invention defined by the claims.

All publications, patents, and patent applications cited in thisspecification are herein incorporated by reference in their entirety asif each publication, patent, or patent application were specifically andindividually put forth herein. In addition to the publications, patents,or patent applications recited above, the following references arehereby incorporated by reference for technical disclosures relating toone or more steps of embodiments of the invention: U.S. Pat. No.3,810,365, U.S. Pat. No. 5,665,319, and publications US20100018218,US2011290162, US20110260112, CN202485229U, CN103357265, and CN102764577.

Where methods and steps described above indicate certain eventsoccurring in certain order, those of ordinary skill in the art willrecognize that the ordering of certain steps may be modified and thatsuch modifications are in accordance with the variations of theinvention. Additionally, certain of the steps may be performedconcurrently in a parallel process when possible, as well as performedsequentially.

Therefore, to the extent there are variations of the invention, whichare within the spirit of the disclosure or equivalent to the inventionsfound in the appended claims, it is the intent that this patent willcover those variations as well. The present invention shall only belimited by what is claimed.

What is claimed is:
 1. A process for transforming energy as available toenergy on demand using said energy as available to convert startingcarbon oxide to overall reaction products consisting essentially ofcarbon and diatomic molecular oxygen, separately oxidizing at least someof said carbon to generate said energy on demand and consequent carbonoxide, and employing a plurality of cycles comprising recycling and/orreusing said consequent carbon oxide, either in actuality or virtuallyvia the atmosphere, wherein each of said plurality of cycles includes(i) reducing at least some of said consequent carbon oxide to generaterecycled carbon and additional diatomic molecular oxygen, with no otherproducts of overall reaction, and (ii) oxidizing at least some of saidrecycled carbon to generate additional energy on demand, wherein saidprocess further comprises intermediate storage of said carbon.
 2. Theprocess of claim 1, wherein at least a portion of said starting carbonoxide is obtained, directly or indirectly, from said atmosphere.
 3. Theprocess of claim 1, wherein said energy as available is selected fromthe group consisting of fossil-fuel energy, wind energy, solar energy,biomass energy, moving-water energy, geothermal energy, nuclear energy,and combinations thereof.
 4. The process of claim 1, wherein said energyas available is renewable energy.
 5. The process of claim 1, whereinsaid energy as available directly provides energy, heat, or work toreduce said carbon oxide to said carbon.
 6. The process of claim 1,wherein said energy as available is converted to secondary energy, andwherein said secondary energy provides energy, heat, or work to reducesaid carbon oxide to said carbon.
 7. The process of claim 6, whereinsaid secondary energy is electricity.
 8. The process of claim 1, whereinsaid energy as available directly or indirectly provides at least aportion of said carbon oxide to said process.
 9. The process of claim 1,wherein said energy as available is biomass energy that is associatedwith generation of biomass-derived carbon oxide, and wherein saidbiomass-derived carbon oxide is used as or combined with said carbonoxide.
 10. The process of claim 1, wherein said carbon oxide isconverted to a reduced stream consisting essentially of said carbon andsaid diatomic molecular oxygen by a reduction reactor operated ateffective reduction conditions.
 11. The process of claim 10, whereinsaid effective reduction conditions are provided by chemical, catalytic,thermal, electrical, dielectrical, ionic, plasma, electrochemical,electromagnetic, or photocatalytic means, or a combination thereof. 12.The process of claim 10, wherein said reduction reactor is selected fromthe group consisting of a thermal reactor, a catalytic reactor, anelectrolysis reactor, a reverse fuel cell, an electrochemical reactor,an electromagnetic reactor, a photocatalytic reactor, a pulsed laserreactor, and a plasma reactor.
 13. The process of claim 1, wherein saidcarbon oxide comprises carbon monoxide, and wherein said effectivereduction conditions promote the carbon-forming Boudouard reaction. 14.The process of claim 1, wherein said carbon oxide is converted to areduced stream consisting essentially of said carbon and said diatomicmolecular oxygen in a reduction reactor operated at effective reductionconditions, and wherein said process comprises separating said carbonfrom said diatomic molecular oxygen in a separation unit that isoptionally integrated with said reduction reactor.
 15. The process ofclaim 1, wherein said carbon is densified.
 16. The process of claim 1,said process further comprising supplementing said carbon with anothercarbon source, initially and/or continuously.
 17. The process of claim1, said process further comprising transporting at least a portion ofsaid carbon to an oxidation reactor.
 18. The process of claim 17,wherein said at least a portion of said carbon is transported by atransporting means selected from the group consisting of truck, train,ship, barge, pipeline, bulk solids conveyer, and combinations thereof.19. The process of claim 17, wherein said at least a portion of saidcarbon is transported by forming a slurry of carbon in liquid oxygen.20. The process of claim 1, wherein a common reactor is utilized toreduce said carbon oxide to said carbon and then to oxidize said carbonto said consequent carbon oxide.
 21. The process of claim 1, whereinsaid intermediate storage is selected from the group consisting ofpiles, rail cars, truck trailers, tanks, silos, bins, hoppers,intermediate bulk containers, sacks, drums, and combinations thereof.22. The process of claim 1, wherein said carbon is oxidized with anoxidant.
 23. The process of claim 22, wherein said oxidant includesoxygen is obtained from said oxygen.
 24. The process of claim 22,wherein said oxidant is obtained from air.
 25. The process of claim 22,wherein said oxidant is a metal oxide or another compound containing ametal and oxygen.
 26. The process of claim 22, said process furthercomprising transporting said oxidant from a reduction reactor to anoxidation reactor.
 27. The process of claim 22, said process furthercomprising intermediate storage of said oxidant.
 28. The process ofclaim 27, wherein storage is selected from the group consisting of apiles, rail cars, truck trailers, tanks, silos, bins, hoppers,intermediate bulk containers, sacks, drums, the atmosphere, andcombinations thereof.
 29. The process of claim 1, said processcomprising oxidation of said carbon in an oxidation reactor operated ateffective oxidation conditions to generate reaction energy and anoxidized stream comprising said consequent carbon oxide.
 30. The processof claim 29, wherein said oxidation reactor is selected from the groupconsisting of a boiler, a conventional coal-fired power plant, amodified coal-fired power plant, a non-catalytic combustion unit, acatalytic oxidation reactor, a chemical-looping combustion system, afuel cell, and an integrated gasification combined cycle unit.
 31. Theprocess of claim 30, wherein said oxidation reactor is a moltencarbonate or solid oxide fuel cell.
 32. The process of claim 29, whereinsaid reaction energy is directly recovered as said energy on demand. 33.The process of claim 29, wherein said reaction energy is converted tosaid energy on demand.
 34. The process of claim 1, wherein said energyon demand is selected from the group consisting of electrical energy,mechanical energy, thermal energy, chemical energy, electromagneticenergy, and combinations thereof.
 35. The process of claim 1, whereinsaid energy on demand is dispatchable renewable energy and/ordistributable renewable energy.
 36. The process of claim 1, wherein allof said carbon is oxidized to generate said energy on demand and saidconsequent carbon oxide.
 37. The process of claim 1, wherein saidrecycling and/or reusing said consequent carbon oxide is in actuality.38. The process of claim 1, wherein said recycling and/or reusing saidconsequent carbon oxide is virtually via said atmosphere.
 39. Theprocess of claim 1, wherein all of said carbon oxide is provided by saidrecycling and/or reusing said consequent carbon oxide.
 40. The processof claim 1, wherein essentially all (except for process losses) of saidconsequent carbon oxide is recycled and/or reused.
 41. The process ofclaim 1, said process further comprising intermediate storage of saidconsequent carbon oxide.
 42. The process of claim 41, wherein saidstorage is selected from the group consisting of rail cars, trucktrailers, tanks, silos, bins, hoppers, intermediate bulk containers,sacks, drums, the atmosphere, and combinations thereof.
 43. The processof claim 1, wherein said energy as available is co-located with saidenergy on demand at a single plant site.
 44. The process of claim 1,wherein said energy as available and said energy on demand are locatedat separate plant sites.
 45. The process of claim 1, wherein saidprocess generates essentially no net carbon emissions.
 46. A process fortransforming renewable wind or solar energy as available to dispatchableenergy on demand, said process comprising: (a) using said renewable windor solar energy as available, in electron, photon, plasma, or thermalform, to reduce carbon oxide to overall reaction products consistingessentially of carbon and diatomic molecular oxygen; (b) increasing bulkdensity of said carbon; (c) storing said carbon; (d) separatelyoxidizing at least some of said carbon to generate said energy on demandand consequent carbon oxide; and (e) recycling and/or reusing saidconsequent carbon oxide, either in actuality or virtually via theatmosphere, wherein said process is characterized by essentially zeronet carbon emissions.